Method of and apparatus for synchronization



Aug. 30, 1932. J. H. HAMMOND, JR 1,374,237

METHOD OF AND APPARATUS FOR SYNCHRONIZATION Original Filed lay 22, 1929 2 Sheets-Sheet l Q 0 o o o o u o o 0 o o o 0 o 0 0 I E" 0 0 O 0 0 O o o f o 0 0 0 i I 0 I J. Q '0 0 o o o 0 o o 0 Q i 0 0 o o o o o 0 ml 2 o 0 I 0 O O I I r I} o 0 I "0 o o o v H 30 0 0 0 0 o O 0 o I C O 1, 2 0 a 0 w q a I o o o 0 o o 0 o o 0 o o o 0 o a INVENTOR JOHN HKYS HAMMOND JR.

ATTORNEY 1932- J. H. HAMMOND, JR 1,374,287

METHOD OF AND APPARATUS FOR SYNCHRONIZATION Original Filed llay 22, 1929 2 Sheets-Sheet 2 BY 7%A/mH ATTORNEY Patented Au 30, 1932'- JOHN HAYS HAMMOND, 33.,

er owners-ran, mssacmrsms METHOD OF AND APPARATUS I'OB BYNOHRONIZATION Application am my 2:, 1m, mm In; aura. Renewed January 0, 10:1.

The object of this invention is to provide a method and apparatus for synchronizing a receiver for television or picture transmission by means of impulses sent from a transmitter for cooperating therewith.

More in particular, the object of this invention is to produce synchronization of a receiver for television or picture transmission by means of picture elements symmetrically arranged relative to the picture it is de sired to transmit. e

Other objects will become apparent from the following specification taken in connection with the appended drawings.

The system embodying this invention uses synchronizing impulses which may be projected as a frame around the picture, so that it is not necessary to use a separate channel for synchronizing. The impulses used for synchronization need not necessarily be separated out from the picture.

Other systems having a similar pur ose have not been successful because of the ack of selective features of the synchronizing channel, that is, lack of ability to choose the proper impulses to operate the synchronizing mechanism. The v present system, however, provides a selective type of pattern by which the synchronization elements of the picture may be readily and accurately difierentiated from the other elements of the picture not intended to influence the synchronization.

In one embodiment of the invention, a frame is made up of the picture elements in such a manner as to give an accurate time interval between the successive impulses Which-make up the frame. Thus the frame may take the form of a double row of dots surrounding the picture on all sides. When the central portion of the picture and the frame thus provided-is being scanned, between the upper and the lower frames, there will occur four dots in sequence, namely two dots at the end of the right border or end of one line and two dots at the beginning or left border of the succeeding line. The time in terval between the successive dots should be equal. At the top and bottom of the picture,

the number of dots will be much greater as though the dots the four lines of dots follow in succession that is the two lines of dots at the bottom of the picture and the two lines at the top of the next picture and also the two dots at the, right border of the next dots at the left border of the next succeedingline. In this case also the time interval between all of the dots will be the same alare at widely separated parts of the picture.

As an illustrative example, with 12 dots to a line and 24 lines to a picture, and with a speed of transmission of 15 pictures per second, the time interval between the successive dots will be 1/4320 seconds even if one dot corresponds to the end of one picture and the next corres onds to the beginning of the next picture. he occurrence of picture elements at the rate of 4320 impulses per second indicates that these dots are intendedfor synchronization. The occurrence of a sequence of four such elements indicates the ending of one line and beginning of the next, with the exact transition occurring in the middle of the sequence. Such sequences occur at line frequency of 360 sequences per second, but a sequence of 52-dots indicates the end of one picture and the be 'nnin of the next, with the transition at-t e mi dle of the sequence, and such sequences would occur 15 times per second. In other words, three selective timings b means of the frame elements are provided; rst, the regular spacings of dots which serves to differentiate the portion of the picture to be used for synchronization from all other portions of the picture; second, groups of a few dots occurring at line frequency which are used for the lateral framing; and, third, groups of a lar e number of dots at picture frequency to fie used'for vertical framing. These dots ma be transmitted by using a suitable background for the objects being televised or by use of special holes or other accurately timed devices at a portion of the transmitter scanner not being used for picture pick-up.

Utilization of the framing dots may involve tuning to the dot frequency to select out the synchronizing elements, followed by detection to produce a current of line frepreceding line and the two i quency to control the lateral framing, and a current of picture frequency tocontrol the vertical framing. The driving mechanism for the receiver scanner may be arranged to generate currents having similar frequencies and by matching the locally generated currents a ainst the incoming currents a correcting impulse may besupphed to the drivingmotor for thus automatically maintainthe frame.

aving thus briefly described my invention, attention is invited to the accompanying drawings in which:

Fig. 1 is a picture or scene adapted to betransmitted and supplied with the framing elements or dots; an

QFi 2 represents the circuit for accomplishmg the synchronism in accordance with I my invention.

Referring now more particularly to Fig. 1, a picture'is shown which is composed of the scene to be transmitted and the framin dots.

As above described and here illustrate this picture may consist of 12 dots to a line and 24 lines to a picture and if the pictures are sent at the rate of 15 pictures per second, the successive dots occurring in the upper and lower margin would be transmitted at the rate of 4320 impulses per second.

Referring now more particularl to Fig. 2, 1 re resents a radio receiver an amplifier of t e usual type for picking up the-transis inductively coupled to a tuned circuit 4 which is tuned to the dot frequency and therefore is adapted to transfer only energy of said frequency and to reject energy of the heterogeneous frequencies composing the pic- I ture part of the transmission. -The energy picked u by the circuit 4 is adapted to be detected by the detector 5 and its associated circuits. In the output of the detector 5 there isa tuned circuit 6 which is tuned to the line frequency or the frequency'with which the succession of four dots will occur in the transmission, viz., the two at the right end of one line and the two at the left end of the succeeding line. Also in the output of the detector 5 is the oscillatory circuit 7 which is tuned to the picture frequency of, say, 15 per second.

Inductively related to the inductance of the circuit 6 is an inductance connected to the armature exciting coil of the polarized relay 8 and inductively related to the inductance of to be controlled the oscillatory. circuit 7 is an inductance-con- The motor 10 is for drivin the recordingapparatus or the scanning dis 13, as shown,

mounted on the same shaft with the motor 10 and the generators 11 and 12. The gen erator 11 is adapted to generate a frequency which is the same as theline frequency being transmitted, provided the speed of the motor 10 is correct. The generator 12 is adapted to generate a frequency which is the same as the picture frequency provided the speed of the motor 10 is correct. The output of the generator 11 is sup lied to the field coil 14 of the polarized re ay 8 and the output of the generator 12 is supplied tothe field coil 15 of the polarized relay 9. The current for supplying the motor 10, is supplied through the lines 24 through varying combinations of the resistances 20, 21, 22, and 23, as operated to be cut in and out by the relays 16, 17, 18, and

19, respectively.

Relay 16' is adapted to be operatedby thepolarized relay 8 when the latter is in the right-hand position. Operation of this relay serves to cause the resistance 20 to be included in the circuit of the motor 10.

The relay 17' is adapted to be excited when the polarized relay 8 is in the left-hand posi-' tion and is adapted to cause the resistance 21 to be removed or short circuited from the circuit of motor 10.

The relay 18 is adapted to be excited by the polarized relay 9 when it is in the righthand position and is adapted, when excited, to insert the resistance 22 in the circuit of the motor 10."

The relay 19 is adapted to be excited when 4 the polarized relay 9 is in the left-hand position and is adapted to remove the resistance 23 from the circuit of the motor 10.

Thus, 'when both relays 8 and 9 are to the right, and both relays 16 and'18 are excited," all of the resistances are in the motor circuit.

When, on the other hand, both relays8 and 9 are to the left, relays 17 and 19 are excited and there is no resistance in the motor circuit. When each of the relays 8 and 9 are in neutral, none of the relays 1619 are excited and resistances 21 and 23 are included in the motor circuit. This is the normal running position and a supplementary rheostat may be provided in the motor circuit to give the rough adjustment of the proper speed for that condition.

Having thus described my invention, I will now describe its operation. If the motor 10 and generators advance in phase with respect to the received current, the line frelished. Thus the right-hand contacts. This causes resistances 20 and 22 to be included in the motor circuit and serves to slow it down. On the other hand, if the motor gets behind in phase with respect to the transmitting current, the relays 8 and 9 will be moved to the left, causing the resistances and 23, which are normally included in the motor circuit, to be removed therefrom, increasing the speed of the motor until synchronization is ob tained. I

It is obvious that when the system is first started up, the transmitter and receizer will not be in step, and therefore the relays will be in operatlon until synchronism is estabthe system here shown is automatic not only for'maintaining the pro er framing, but for obtaining'it in the rst place. It is obvious that the system ma be further elaborated as, for example, ma ing the resistance inserted or extracted from the motor circuit proportional to the phase difference in the incoming and local currents.

The li' ht adapted to be actuated by the amplifirf""2,-fyill be caused to operate in ac.- cordancefwith the dots which are meant entirely for framing and it will be necessary to limit the area scanned by the electrically controlled lamp in connection with the scanning disk 13 to the picture part of the transmission by the insertion of some frame between the light source and the observing screen. In the recording of the pictures, either the negative upon which the light is adapted to be impressed may be so small as to only include the picture impulses or the light pulses or the negative produced by the framing dots may be trimmed or framed out in printing, etc.

Having thus described my'invention, it is to be understood that the form is shown and described herein for the purpose of illustration only, and that I am not to be limited by the specific embodiment shown, but by the scope of my invention as set forth and defined in the accompanying claims.

I claim p 1. A framing and synchronizing systemwhich involves producing a pattern of picture elements which will not interfere with the picture, said elements producing a regular se- Felectively tuning these time elements from the other picture elements, means for detecting and producing currents of group frequencies corresponding to a picture frequency and also corresponding to line frequencies, means for actuating a reproducing device, means for producing a group frequency corresponding to the picture frequency, and neans for producing a group frequency corresponding to the line frequency by the rotation of said last mentioned means, means for matching the incoming picture frequencies against the localeach of substantiall fluctuations covering the picture im- 1y generated picture frequencies in such'a manner as to control the speed of the actuatmg means to maintain the received picture bem framed.

2 lhe method of. synchronization for picture transmission which comprises, transmitting a series of impulses re resenting'the picture to be transmitted and including a pattern producing distinctive frequencies, receiving said transmission, tunin to the distinctive frequencies, detecting sai frequencies to produce line frequencies and picture frequencies," locall 'generatin line frequencies and picture requencies 111' synchronism with the reproducin rotation, and com aring said 10- cally pr uced andreceived l ine frequencies and said locally producedand received icture frequencies to control the speed of sai producing rotation.

' 3. A method of transmittingpicture sigmale and framing impulses which comprises transmitting in a line for line manner signals light and shadow representing the intensity of on each elemental area of each line of the picture, transmitting a series of horizontal framing signals at the end of each line of signals 7 representing intensities of light and shadow on the record, and transmitting at the end of the series of si als representing the intensity of light and s adow on all linesof the picture and the signals indicating horizontal framing a series of vertical framing signals the same amplitude and duration as the honzontal signals and distinguishable therefrom by the period of duration. Y 4. A method of transmitting picture si nals and synchronizing impulses for controd ling the position of the picture signals at the receiver which comprises transmitting in a line for line manner signals representing the intensity of light and shadow on each elemental areaof each line of the picture, transmitting at the end of each line of signals representing intensities of light and shadow on the record for transmission a series of equal amplitude signals to serve as horizontal synchronizin indications, and transmitting at the end of the series of signals representing the intensity of light and shadow on all lines of the picture. and the horizontal synchronizing signals separate series of signals of time ries of group impulses, comprising, means for duration exceedin the of amplitude an individual duration substantially equal to each horizontal signal to serve asvertical synchronizing signals 5. In a television system for transmitting signals to represent, when re roduced, an im-, age of an ob act at a transmitter, the method of transmission which comprises transmitting als varying in proportion to the intensity horizontal signals and $1 0 light and shadow on elemental areas of a series of lines into which the subject for transmission is assumed to be divided, transmitting as separated signalling impulses at the en of each line of transmission of signal indications of light intensity a series of se arated signals for indicating horizontal frammg, and transmitting at the end of all of said series of signal indications representing light intensities for each line of t sion and the horizontal framing indications therefor an additional series of signal indications each of intensit and frequency of interruption correspon ing to the horizontal signals but of materially reater duration for indicating vertical fram ng position of the subject for transmission.

6. In a television system for transmitting signalling indications representing successive light intensities on a sub ect for transmission and framing indications for indicating the relative position of said light indications, means for transmitting in a line for line manner signal representations corresponding to the varying intensities of light and shadow on each elemental area of the subject for transmission, means for transmitting at the end of eachline of light intensity indications of the subject for transmission a plurality of signals each of like time separation for representing horizontal framing, and means for transmitting at the end of a complete series of indications of light intensity and the coordinated horizontal framing indications a relatively long series of signals each of like time separation for indicating vertical framing.

7. In a television system for pro ucing at a receiving system an electro-optical image of a subject at a transmitter wherein signals representing the varying intensities of ight and shadow {or each elemental area of the subject at the transmitter are separated in a line for line manner by horizontal framing indications and at the end of transmission of a seriesof picture lines by vertical framing indications, the method of reproducing the picture which comprises producing from the picture signals indications of light ,and

shadow (proportionate'to the indications of light an shadow on each elemental area of the subject for transmission, causing the signals received at the end of each line of signal indications of light value for the subject at the transmitter to differentially vary and control the horizontal framing of the received light impressions, and causing signals representing the vertical framing to difi'erentially adjust the vertical position ofall of the received light indications complete series thereof.

8 In a television system for producing at a receiving system an electro-optical image of a subject at a transmitter wherein signals representing the varying intensities of light at the end of a and shadow for each'elemental area of the subject at the transmitter are separated in a line for line manner by" horizontal synchronizing indications and at the end of-complete transmission of aseries of intensity e subject for transmisconstructing an electro-optical image of producing the picture which comprises producing from the light controlled signals indications of li ht and 'shadow pro ortionate to the indicat1ons of li ht and s adow on each elemental area of t e subject for transmission, causing the signals received at the end of each line of signal indications of light value for the subject at the transmitter to differentially vary and control the horizontal synchronization of the received light impressmns, and causing signals representing the vertical synchronizing pulses to diff ferentially adjust the vertical position of all of the received li ht indications 'at the end of a complete serles thereof.

9. A method for synchronizing picture transmission which comprises transmitting a series of impulses representing varying intensities of hght and shadow on elemental areas of'a s11 ject at a transmitting point, transmittin distinctive frequencies representing horizontal and vertical framing positions of the subject at the transmitter, receiving said transmitted series of impulses, locally controlling the signal reproduction for producing an electro-optical ima e of the subject at the transmitter, and di erentially controlling the locally controlled signal reproduction for framing the received signals both horizontally and vertically upon variance of the locally controlled reproduction from the rate of transmission of values of elemental areas of a subject at atransmitter and signal indications of dis-- 05 tinct frequency representing horizontal and vertical synchronization thereof, meansfor producing ,from the signal indications of hght-values corresponding light values for a subject at the transmitting point, means at the receiving point for locally controlling the relative position at which said light values are reproduced at the receiver, means for differentially controlling the position of said light reproduction at the end of, each line of received light intensity indications for horizontally synchronizing the received light indications, and means for differentially controlling in response to vertical synchronizing indications the vertical position. of the complete series of light indicationsafter a complete series of light intensity indications and horizontal synchronizing indications of the entire subject at the 'transmit- 25 ter have been received.

- JOHN HAYS HAMMOND, JR. 

